The EU nationals traveling to Syria cause authorities’ concern,
as the European governments fear they may return and carry out
attacks on home soil.

At least one European, Mehdi Nemmouche, participated in such an
attack, and suspected of killing four people in Jewish Museum in
Brussels last year.

"At the time of the attacks in Paris and Copenhagen, we
decided not to allow ourselves to be guided by fear,"
Jourova said, speaking of January’s deadly assaults in the French
capital, and the fatal shootings in Denmark a month later.

The reasons behind the Europeans leaving are “a desire for
adventure, boredom, dissatisfaction with their situation in life
or a lack of prospects,” a UK research conducted to look
into the matter has found, according to the Commissioner.

She added that the EU is accelerating the sharing between police
forces and court systems of different states, plus there is an
increase in intelligence exchange.

"We want the exchange of information to intensify between
Europol and Eurojust [judicial cooperation unit of the EU],"
and this exchange should become “systematic and
automatic,” Jourova said.

For that, "joint investigation teams are created so that
prosecutors and police officers from several EU countries can
work together."

Islamic State (also known as ISIS, or ISIL) currently has control
over a significant amount of territory in Syria and Iraq, and has
attracted thousands of foreigners to fight in their ranks.